fn widen_slice(
nal: &[u8],
narrow: u32,
idr: bool,
last: u32,
) -> Option<(u32, Vec<u8>)>Expand description
A slice under a widened set, and its widened frame_num: the encoder’s narrow bits numbered
on from last, the widened value of the slice before it, with the byte above them inserted
ahead.